PACCAR Updates MX-11 and MX-13 Engine Software to Comply with Revised EPA Guidance on DEF Inducements
PACCAR is updating software for Kenworth and Peterbilt trucks to align with new EPA guidance, increasing the final inducement speed from 5 to 25 mph and extending the timeline before that speed from 4 to 160 hours.
5 to 25 mph
4 to 160 hours
July 20, 2026
What Happened
PACCAR Inc. has announced software updates for the MX-11 and MX-13 engines used in Kenworth and Peterbilt trucks, following revised guidance from the U.S. Environmental Protection Agency (EPA) on Diesel Exhaust Fluid (DEF) inducements. Trucks manufactured after July 20, 2026 will have the update from the factory, and trucks built after 2018 can get it at dealerships. The changes are designed to improve reliability and reduce unnecessary operational disruptions.
- 5 mph → 25 mph
- 4 hours → 160 hours
- Final inducement speed limit increased from 5 mph to 25 mph
- Timeline extended from 4 to 160 hours before reaching final inducement speed
- Software installed on trucks manufactured after July 20, 2026
- Updates available at Kenworth and Peterbilt dealerships for trucks built after 2018
DEF inducements are safeguards that reduce vehicle speed and power when emissions system issues are detected, such as low DEF levels or reduced Selective Catalytic Reduction (SCR) system performance. They prompt drivers to correct the issue by refilling DEF, repairing sensors, or performing system regeneration. All MX-powered vehicles remain subject to EPA emissions requirements and must be serviced for compliance.
Why this matters
This software update helps truck owners by reducing unnecessary disruptions from DEF inducement systems, which can slow vehicles when emissions issues arise. The changes mean drivers have more time and higher speed to address problems like low DEF levels, potentially avoiding roadside stops. For fleet operators, this translates to improved reliability and fewer operational delays.
Terms in This Story
- DEF (Diesel Exhaust Fluid)
- A fluid injected into exhaust systems to reduce nitrogen oxide emissions.
- SCR (Selective Catalytic Reduction)
- An emissions control system that uses DEF to convert pollutants into harmless gases.
- DEF inducement
- A safeguard that reduces vehicle speed and power when emissions system issues are detected.
Summarised from the linked release; details can be imperfect — always verify against the original source.